Is it correct to dynamically add rows to a table (in sqlite), or should I use csv?

Just like when adding a new contact in the ios contact app, (like this) you can add multiple phone numbers, and it doesn't know how many there will be, so therefore they don't know how many rows they should initially add in the table of sqlite.

So how does that work, do they dynamically add rows to the table, or do they use csv?

(I'm using objective c)